From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Wed, 28 Jan 2009 20:02:03 +1100

One thing that I've been thinking about is that it would be
really useful if we guaranteed that every inbound packet carried
a hash with it.  This could be used to help subsequent processing
such as routing, netfilter, etc. since they all need to make
decisions based on flows.

Ok, all the complicated cases will have to occur in decapsulators :-)

For example, IP tunnels would need to compute the hash as would most
forms of IPSEC since often we can't even see the inner flow until
after decryption even for transport cases.